Overview

Tursiops truncatus – (Montagu, 1821)

ANIMALIA – CHORDATA – MAMMALIA – ARTIODACTYLA – DELPHINIDAE – Tursiops – truncatus 

Common Names: Common Bottlenose Dolphin, Bottlenosed Dolphin, Bottlenose Dolphin, Bottlenosed Dolphin (English), Stompneusdolfyn (Afrikaans), Afalina (Turkish), Dauphin souffleur, Grand dauphin, Souffleur (French), Delfin Geddumu Qasir (Maltese), Delfin I Madh (Albanian), Delfin Kabir (Arabic), Delfín Mular (Spanish; Castilian), Dobri dupin (Croatian), Golfinho-roaz (Portuguese), Grosser Tümmler (German), Tursiope (Italian), Velika pliskavka (Slovenian), Ρινοδέλφινο (Rinodélfino) (Greek, Modern (1453-)
Synonyms: Delphinus truncatus Montagu, 1821; Tursiops nuuanu Andrews, 1911  

Taxonomic Note: 
The taxonomy of the genus Tursiops remains unresolved. Consequently, there is confusion in the literature between Tursiops species, not only in respect of taxonomy, but also natural history. In many regions across its distribution two forms of bottlenose dolphins have been described: an offshore form and a coastal form. Although many of their characteristics overlap, morphological and mitochondrial differences between these two regional forms have been recognised (Ross 1977; Hoelzel et al. 1998). In South African waters, Ross (1977) described two allopatric species based on morphological differences: the smaller, coastal form, T. aduncus, and the larger offshore form, T. truncatus. Hoelzel et al. (1998) compared mitochondrial and nuclear genetic markers between nearshore and offshore types of bottlenose dolphins in a range of geographic locations. Although, Hoelzel et al. (1998) described a clear distinction between the coastal and offshore forms of bottlenose dolphins in the western Pacific, no such distinction was identified between the larger offshore form (T. truncatus) and the smaller inshore form (sometimes referred to as T. aduncus) off southern Africa. Hoelzel et al. (1998) suggest that the separation between these forms off Africa may be comparatively recent, or some degree of gene flow between the populations may still exist. Additionally, Ross and Cockcroft (1990) suggest that the two forms should not be delineated as separate species. Generally, where they occur in the same geographic areas T. truncatus has a longer body, larger skull and less teeth than T. aduncus (Ross 1977; Gao et al. 1995). Both species show sexual dimporphism, with males larger than females (Cockcroft & Ross 1990; Hale et al. 2000). In this assessment, we consider only the offshore T. truncatus, while T. aduncus is assessed separately. There is likely to be further fine scale resolution of the genus in future, as research progresses. 

Red List Status: LC – Least Concern, (IUCN version 3.1) 

Assessment Information

Assessors: Probert, R.¹, & da Silva, J.² 

Reviewer: Plön, S.¹ 

Institutions: ¹University of Cape Town, South Africa, ²South African National Biodiversity Institute 

Previous Assessor: Plön, S. 

Previous Reviewer: Cockcroft, V. 

Previous Contributors: Findlay, K., Oosthuizen, H., Meyer, M., Elwen, S., Relton, C., Child, M.F. & Atkins, S. 

Assessment Rationale 

The Common Bottlenose Dolphin is widespread and abundant throughout its range and regular sightings and strandings within the assessment region suggest that there is no major population decline and no immediate major threats are suspected. However, shifts in climatic conditions over the years may be of concern, although there is insufficient data to support this thus far. In contrast to T. aduncus, which is commonly accepted as the coastal resident population of bottlenose dolphins, T. truncatus is considered to occur largely offshore. Anthropogenic disturbance in the form of boat traffic, fisheries and ecotourism, as well as pollution (including noise, plastic debris and persistent organic pollutants) are recognised as minor threats to this species. Common Bottlenose Dolphins are currently not considered a conservation priority and are therefore listed as Least Concern in line with the global listing.

Regional population effects: The Common Bottlenose Dolphin exhibits seasonal movements, often following the seasonal migrations of sardine off South Africa’s south and east coasts. There are no barriers to dispersal, thus rescue effects are possible. 

Reasons for Change 

Reason(s) for Change in Red List Category from the Previous Assessment: No change 

Red List Index 

Red List Index: No change 

Recommended citations: Probert R & da Silva JM. 2025. A conservation assessment of Tursiops truncatus. In Patel T, Smith C, Roxburgh L, da Silva JM & Raimondo D, editors. The Red List of Mammals of South Africa, Eswatini and Lesotho. South African National Biodiversity Institute and Endangered Wildlife Trust, South Africa.

Regional Distribution and occurrence

Geographic Range 

Globally, bottlenose dolphins are widely distributed, found throughout tropical and temperate regions, only absent in the extreme high latitudes (Skinner & Chimimba 2005). Two forms are often described, where one is commonly restricted to coastal areas and estuaries, while the other is associated with open ocean areas, usually regions of upwelling and high productivity, such as shelf edges and sea mounts. Across the entire assessment region, the range of the Common Bottlenose Dolphins extends from the Orange River mouth to Kosi Bay, present both in continental shelf waters and inshore, seldomly found in waters shallower than 50m. 

A common assumption is that inshore records in the Indian Ocean belong to T. aduncus, while T. truncatus is only found further offshore (Best 2007). Findlay et al. (1992) describes the presence of T. truncatus offshore on the south and southeast coast, as well as inshore on the west coast of South Africa. 

In the southwest Atlantic a coastal population of T. truncatus occurs off Namibia, usually found in waters less than 10 m deep. It has been reported from waters between Cape Cross and Walvis Bay, but the geographical limits of its range remain largely uncertain (Best 2007). This is the only resident coastal population of this species in southern Africa (Namibia, South Africa and Mozambique); elsewhere off the South African coast this species is usually found in waters less than 100 m deep, as well as at depths of between 500 m and 1,000 m (Best 2007).  

Elevation / Depth / Depth Zones 

Elevation Lower Limit (in metres above sea level): NA 

Elevation Upper Limit (in metres above sea level): NA 

Depth Lower Limit (in metres below sea level): 1000 m 

Depth Upper Limit (in metres below sea level): 0 m 

Depth Zone: (Not specified) 

Map

Figure 1. Distribution records for Common Bottlenose Dolphin (Tursiops truncatus) within the assessment region (South Africa, Eswatini and Lesotho). Note that distribution data is obtained from multiple sources and records have not all been individually verified.

Biogeographic Realms 

Biogeographic Realm: Afrotropical, Australasian, Indomalayan, Nearctic, Neotropical, Oceanian, Palearctic 

Occurrence 

Countries of Occurrence 

Country	Presence	Origin	Formerly Bred	Seasonality
Albania	Extant	Native	–	Resident
Algeria	Extant	Native	–	Resident
American Samoa	Extant	Native	–	Resident
Angola	Extant	Native	–	Resident
Anguilla	Extant	Native	–	Resident
Antigua and Barbuda	Extant	Native	–	Resident
Argentina	Extant	Native	–	Resident
Aruba	Extant	Native	–	Resident
Australia	Extant	Native	–	Resident
Bahamas	Extant	Native	–	Resident
Bahrain	Extant	Native	–	Resident
Bangladesh	Extant	Native	–	Resident
Barbados	Extant	Native	–	Resident
Belgium	Extant	Native	–	Resident
Belize	Extant	Native	–	Resident
Benin	Extant	Native	–	Resident
Bermuda	Extant	Native	–	Resident
Bonaire, Sint Eustatius and Saba	Extant	Native	–	Resident
Bosnia and Herzegovina	Extant	Native	–	Resident
Brazil	Extant	Native	–	Resident
British Indian Ocean Territory	Extant	Native	–	Resident
Brunei Darussalam	Extant	Native	–	Resident
Bulgaria	Extant	Native	–	Resident
Cabo Verde	Extant	Native	–	Resident
Cambodia	Extant	Native	–	Resident
Cameroon	Extant	Native	–	Resident
Canada	Extant	Native	–	Resident
Canada -> Newfoundland I	Extant	Vagrant	–	–
Cayman Islands	Extant	Native	–	Resident
Chile	Extant	Native	–	Resident
China	Extant	Native	–	Resident
Christmas Island	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Cocos (Keeling) Islands	Extant	Native	–	Resident
Colombia	Extant	Native	–	Resident
Comoros	Extant	Native	–	Resident
Congo	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Congo, The Democratic Republic of the	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Cook Islands	Extant	Native	–	Resident
Costa Rica	Extant	Native	–	Resident
Croatia	Extant	Native	–	Resident
Cuba	Extant	Native	–	Resident
Curaçao	Extant	Native	–	Resident
Cyprus	Extant	Native	–	Resident
Côte d’Ivoire	Extant	Native	–	Resident
Denmark	Extant	Native	–	Resident
Djibouti	Extant	Native	–	Resident
Dominica	Extant	Native	–	Resident
Dominican Republic	Extant	Native	–	Resident
Ecuador	Extant	Native	–	Resident
Egypt	Extant	Native	–	Resident
El Salvador	Extant	Native	–	Resident
Equatorial Guinea	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Eritrea	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Falkland Islands (Malvinas)	Extant	Native	–	Resident
Faroe Islands	Extant	Native	–	Resident
Fiji	Extant	Native	–	Resident
France	Extant	Native	–	Resident
French Guiana	Extant	Native	–	Resident
French Polynesia	Extant	Native	–	Resident
Gabon	Extant	Native	–	Resident
Gambia	Extant	Native	–	Resident
Georgia	Extant	Native	–	Resident
Germany	Extant	Native	–	Resident
Ghana	Extant	Native	–	Resident
Gibraltar	Extant	Native	–	Resident
Greece	Extant	Native	–	Resident
Grenada	Extant	Native	–	Resident
Guadeloupe	Extant	Native	–	Resident
Guam	Extant	Native	–	Resident
Guatemala	Extant	Native	–	Resident
Guernsey	Extant	Native	–	Resident
Guinea	Extant	Native	–	Resident
Guinea-Bissau	Extant	Native	–	Resident
Guyana	Extant	Native	–	Resident
Haiti	Extant	Native	–	Resident
Honduras	Extant	Native	–	Resident
Hong Kong	Extant	Native	–	Resident
India	Extant	Native	–	Resident
Indonesia	Extant	Native	–	Resident
Iran, Islamic Republic of	Extant	Native	–	Resident
Iraq	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Ireland	Extant	Native	–	Resident
Isle of Man	Extant	Native	–	Resident
Israel	Extant	Native	–	Resident
Italy	Extant	Native	–	Resident
Jamaica	Extant	Native	–	Resident
Japan	Extant	Native	–	Resident
Jersey	Extant	Native	–	Resident
Jordan	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Kenya	Extant	Native	–	Resident
Kiribati	Extant	Native	–	Resident
Korea, Democratic People’s Republic of	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Korea, Republic of	Extant	Native	–	Resident
Kuwait	Extant	Native	–	Resident
Lebanon	Extant	Native	–	Resident
Liberia	Extant	Native	–	Resident
Libya	Extant	Native	–	Resident
Macao	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Madagascar	Extant	Native	–	Resident
Malaysia	Extant	Native	–	Resident
Maldives	Extant	Native	–	Resident
Malta	Extant	Native	–	Resident
Marshall Islands	Extant	Native	–	Resident
Martinique	Extant	Native	–	Resident
Mauritania	Extant	Native	–	Resident
Mauritius	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Mayotte	Extant	Native	–	Resident
Mexico	Extant	Native	–	Resident
Micronesia, Federated States of	Extant	Native	–	Resident
Monaco	Extant	Native	–	Resident
Montenegro	Extant	Native	–	Resident
Montserrat	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Morocco	Extant	Native	–	Resident
Mozambique	Extant	Native	–	Resident
Myanmar	Extant	Native	–	Resident
Namibia	Extant	Native	–	Resident
Nauru	Extant	Native	–	Resident
Netherlands	Extant	Native	–	Resident
New Caledonia	Extant	Native	–	Resident
New Zealand	Extant	Native	–	Resident
Nicaragua	Extant	Native	–	Resident
Nigeria	Extant	Native	–	Resident
Niue	Extant	Native	–	Resident
Norfolk Island	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Northern Mariana Islands	Extant	Native	–	Resident
Norway	Extant	Vagrant	–	–
Oman	Extant	Native	–	Resident
Pakistan	Extant	Native	–	Resident
Palau	Extant	Native	–	Resident
Panama	Extant	Native	–	Resident
Papua New Guinea	Extant	Native	–	Resident
Peru	Extant	Native	–	Resident
Philippines	Extant	Native	–	Resident
Pitcairn	Extant	Native	–	Resident
Portugal	Extant	Native	–	Resident
Puerto Rico	Extant	Native	–	Resident
Qatar	Extant	Native	–	Resident
Romania	Extant	Native	–	Resident
Russian Federation	Extant	Native	–	Resident
Réunion	Extant	Native	–	Resident
Saint Barthélemy	Extant	Native	–	Resident
Saint Helena, Ascension and Tristan da Cunha	Extant	Native	–	Resident
Saint Kitts and Nevis	Extant	Native	–	Resident
Saint Lucia	Extant	Native	–	Resident
Saint Martin (French part)	Extant	Native	–	Resident
Saint Pierre and Miquelon	Extant	Native	–	Resident
Saint Vincent and the Grenadines	Extant	Native	–	Resident
Samoa	Extant	Native	–	Resident
Sao Tome and Principe	Extant	Native	–	Resident
Saudi Arabia	Extant	Native	–	Resident
Senegal	Extant	Native	–	Resident
Seychelles	Extant	Native	–	Resident
Sierra Leone	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Singapore	Extant	Native	–	Resident
Sint Maarten (Dutch part)	Extant	Native	–	Resident
Slovenia	Extant	Native	–	Resident
Solomon Islands	Extant	Native	–	Resident
Somalia	Extant	Native	–	Resident
South Africa	Extant	Native	–	Resident
Spain	Extant	Native	–	Resident
Sri Lanka	Extant	Native	–	Resident
Sudan	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Suriname	Extant	Native	–	Resident
Syrian Arab Republic	Extant	Native	–	Resident
Taiwan, Province of China	Extant	Native	–	Resident
Tanzania, United Republic of	Extant	Native	–	Resident
Thailand	Extant	Native	–	Resident
Timor-Leste	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Togo	Extant	Native	–	Resident
Tokelau	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Tonga	Extant	Native	–	Resident
Trinidad and Tobago	Extant	Native	–	Resident
Tunisia	Extant	Native	–	Resident
Turks and Caicos Islands	Extant	Native	–	Resident
Tuvalu	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Türkiye	Extant	Native	–	Resident
Ukraine	Extant	Native	–	Resident
United Arab Emirates	Extant	Native	–	Resident
United Kingdom of Great Britain and Northern Ireland	Extant	Native	–	Resident
United States of America	Extant	Native	–	Resident
Uruguay	Extant	Native	–	Resident
Vanuatu	Extant	Native	–	Resident
Venezuela, Bolivarian Republic of	Extant	Native	–	Resident
Viet Nam	Extant	Native	–	Resident
Virgin Islands, British	Extant	Native	–	Resident
Virgin Islands, U.S.	Extant	Native	–	Resident
Wallis and Futuna	Extant	Native	–	Resident
Western Sahara	Extant	Native	–	Resident
Yemen	Extant	Native	–	Resident

Large Marine Ecosystems (LME) Occurrence 

Large Marine Ecosystems: Benguela Current and Agulhas Current LMEs 

FAO Area Occurrence 

	Presence	Origin	Formerly Bred	Seasonality
21. Atlantic – northwest	Extant	Native	–	–
27. Atlantic – northeast	Extant	Native	–	–
31. Atlantic – western central	Extant	Native	–	–
34. Atlantic – eastern central	Extant	Native	–	–
37. Mediterranean and Black Sea	Extant	Native	–	–
41. Atlantic – southwest	Extant	Native	–	–
47. Atlantic – southeast	Extant	Native	–	–
51. Indian Ocean – western	Extant	Native	–	–
57. Indian Ocean – eastern	Extant	Native	–	–
61. Pacific – northwest	Extant	Native	–	–
67. Pacific – northeast	Extant	Native	–	–
71. Pacific – western central	Extant	Native	–	–
77. Pacific – eastern central	Extant	Native	–	–
81. Pacific – southwest	Extant	Native	–	–
87. Pacific – southeast	Extant	Native	–	–

Climate change

There have been significant shifts in both the Benguela current (Hutchings et al. 2009; Moloney et al. 2013; Jarre et al. 2015) and Agulhas current (Mead et al. 2013; Asdar et al. 2022). Large Marine Ecosystems have been documented over the years, including changes in wind patterns, upwelling regimes, and temperatures. These changes can have both direct and indirect effects on Common Bottlenose Dolphin populations. The average sea surface temperature (SST) in the Agulhas Bank increased by 1.5 °C from the 1980s to the early 2000s (Mead et al. 2013) and is estimated to further increase by 2 °C between 2020 and 2100 (Asdar et al. 2022). The Benguela current is warming at a faster rate of 0.15-0.22 °C per decade (Sweijd and Smit, 2020). Common Bottlenose Dolphins have been reported in waters between 10 and 32 °C. As T. truncatus is highly mobile and inhabits waters with a wide thermal range, it is unlikely that they will be severely impacted by increasing SST, although these changes can impact the distribution across their range. 

Climate change can also exacerbate existing threats to T. truncatus such as habitat loss, prey availability, risks of bycatch, and pollutant concentrations. Increasing SST is linked to coral bleaching and has been documented along the South African coast (Celliers & Schleyer 2002), causing loss of reef habitats which are important for the species. Prey species favourable to T. truncatus have varying sensitivities to climate change. Mullet, a preferred prey item, is extremely sensitive to shifts in sea temperatures causing a change in their distribution along the coastline (James et al. 2016). These shifts, paired with those caused by increased fishing pressures, may decrease prey available to bottlenose dolphins. However, T. truncatus are generalist feeders with varying degrees of dietary and feeding plasticity (Neri et al. 2022). Further investigation into the effects of climate change on prey availability and prey choice is needed to fully understand the magnitude of the overall effect on Common Bottlenose Dolphin populations in the various complex ecosystems in South African waters. Furthermore, a decrease in fish biomass can result in an increase in fishing efforts, increasing the risk of dolphin bycatch and entanglement. Common Bottlenose Dolphins are at risk of pollutant contamination, particularly persistent organic pollutants (POPs), which are known to cause reproductive impairment and immune system suppression in other dolphin species (Borrell & Aguilar 2005). Increased sea temperatures have been shown to influence the metal toxicity in marine species (Langston 1990), although it has not been directly tested in dolphins. 

Overall, climate change can have significant impacts, both direct and indirect, on Common Bottlenose Dolphins, impacting their physical habitat, habitat ranges and distribution, the abundance and distribution of prey, and their general and reproductive health. Shifts in species and prey distribution should be assessed concurrently with the changes in the various ecosystems in South African waters to further understand the effects of climate change on T. truncatus within this region. 

Population

Globally, there are estimated to be more than 600,000 Common Bottlenose Dolphins (Hammond et al. 2012). Groups of several tens of T. truncatus are frequently sighted, along with False Killer Whales (Pseudorca crassidens), in the Plettenberg Bay area. This species is sighted regularly in South African waters, and thus, despite frequent stranding events, no population decline is expected

Continuing decline in mature individuals?	Qualifier	Justification
No	–	–

Extreme fluctuations in the number of subpopulations: Unknown 

Continuing decline in number of subpopulations: Unknown 

All individuals in one subpopulation: Unknown 

Number of mature individuals in population: Unknown 

Number of mature individuals in largest subpopulation: Unknown 

Number of Subpopulations: Unknown 

Current population trend: Stable 

Severely fragmented: No 

Quantitative Analysis 

Probability of extinction in the wild within 3 generations or 10 years, whichever is longer, maximum 100 years: (Not specified) 

Probability of extinction in the wild within 5 generations or 20 years, whichever is longer, maximum 100 years: (Not specified) 

Probability of extinction in the wild within 100 years: (Not specified) 

 

Population Genetics

No population genetic studies have been undertaken on T. truncatus in the assessment region. While the species is currently considered a single population in the area, it is possible subpopulations (genetic structure) is present as has been found for this species in other regions around the world (e.g., Sellas et al. 2005; Segura et al. 2006). Fine scale genomic studies would be useful to confirm this. 

Thus far, there are no population size estimates for T. truncatus within the assessment region, however there are regular sightings of this species in South African waters indicating no apparent population decline. Investigation into population size and genetic differentiation are necessary for a robust population assessment within this region. 

Habitats and ecology

Tursiops truncatus is commonly accepted as the open water form of the bottlenose dolphin. However, there are many exceptions to this rule, and this species may also be frequently located within shallower waters, nearer to the coast. Presumably though, T. truncatus generally makes use of deeper reefs further offshore, whereas T. aduncus is restricted to shallower inshore areas (Hale et al. 2000). Studies off the coast of North America found that this species is generally associated with waters exhibiting surface temperatures between 10°C and 32°C (Wells & Scott 1999). Common Bottlenose Dolphins form schools of between 3–100 individuals, with a general average of approximately 22, and are often associated with other cetacean species, for example the Long-finned Pilot Whale (Globicephala melas) and the False Killer Whale (Skinner & Chimimba 2005).

The stomach contents of two T. truncatus individuals from the Eastern Cape revealed that the dominant prey species was squid (Oregoniateuthis), with hake (Merluccius spp.) and Buttersnoek (Lepidpus caudatus) making up lesser proportions (Ross 1977, 1984). The results from these studies indicate that T. truncatus feeds further offshore when compared to T. aduncus, at least off the Eastern Cape coast (Ross 1984). Off the Western Cape, Sekiguchi et al. (1992) recorded that the diet of T. truncatus comprised of cephalopods (mostly the Cape Hope Squid, Loligo vulgaris reynaudii), and a wide variety of fish (dominated by Southern Mullet, Liza richardsonii, and Cape Horse Mackerel, Trachurus trachurus capensis). However, an updated investigation into the diet of Common Bottlenose Dolphins in various regions of the assessment area is needed, with focus on fishery target species in each respective area, as well as feeding strategies used. Leatherwood (1975) describes the high degree of plasticity associated with feeding behaviour of Tursiops spp. along the west coast of North America, including echolocation techniques, cooperative hunting, and the exploitation of anthropogenic fishing activities (such as depredation).

Mother and calf associations may last as long as 3 to 4 years (Bearzi et al. 1997), which may be a general reflection of the inter-birth interval exhibited by female Common Bottlenose Dolphins. Although females usually only breed every 3–6 years, Connor et al. (2000) described intervals of 2 years off the coast of Florida. Model-based estimates of generation time are 21.1 years (Taylor et al. 2007).

Ecosystem and cultural services: This is the archetype of dolphins and, since most South Africans are unaware of the variety of delphinids, this is typically what they envisage when “dolphins” are mentioned. 

IUCN Habitats Classification Scheme 

Habitat	Season	Suitability	Major Importance?
5.1. Wetlands (inland) -> Wetlands (inland) – Permanent Rivers/Streams/Creeks (includes waterfalls)	–	Marginal	–
9.1. Marine Neritic -> Marine Neritic – Pelagic	–	Suitable	Yes
9.10. Marine Neritic -> Marine Neritic – Estuaries	–	Suitable	Yes
10.1. Marine Oceanic -> Marine Oceanic – Epipelagic (0-200m)	–	Suitable	Yes
13.4. Marine Coastal/Supratidal -> Marine Coastal/Supratidal – Coastal Brackish/Saline Lagoons/Marine Lakes	–	Marginal	–

Life History 

Generation Length: (Not specified) 

Age at Maturity: Female or unspecified: 5-12 (population dependent) 

Age at Maturity: Male: (Not specified) 

Size at Maturity (in cms): Female: (Not specified) 

Size at Maturity (in cms): Male: (Not specified) 

Longevity: (Not specified) 

Average Reproductive Age: (Not specified) 

Maximum Size (in cms): (Not specified) 

Size at Birth (in cms): (Not specified) 

Gestation Time: (Not specified) 

Reproductive Periodicity: (Not specified) 

Average Annual Fecundity or Litter Size: (Not specified) 

Natural Mortality: (Not specified) 

Breeding Strategy 

Does the species lay eggs? No 

Does the species give birth to live young: Yes 

Does the species exhibit parthenogenesis: No 

Does the species have a free-living larval stage? No 

Does the species require water for breeding? No 

Movement Patterns 

Movement Patterns: (Not specified) 

Congregatory: (Not specified) 

Systems 

System: Marine 

General Use and Trade Information

There is no trade of this species within South Africa, although there were three, but currently two pure T. truncatus at uShaka Marine World, KwaZulu-Natal, but this has no effect on the wild populations of this species. 

Subsistence:	Rationale:	Local Commercial:	Further detail including information on economic value if available:
Yes	–	–	–

National Commercial Value: Yes 

International Commercial Value: Yes 

End Use	Subsistence	National	International	Other (please specify)
1. Food – human	true	true	–	–
2. Food – animal	true	true	–	–
13. Pets/display animals, horticulture	–	true	true	–

Is there harvest from captive/cultivated sources of this species? (Not specified) 

Harvest Trend Comments: (Not specified) 

Threats

Around the world, Common Bottlenose Dolphins are vulnerable to both accidental and intentional catch, climate change, habitat degradation (Curry & Smith 1997), as well as disturbance and harassment (often due to ecotourism activities). Within the assessment region, this species is not expected to be at risk of any significant population decline; however, a number of minor threats have been identified, and the combination of these threats may become a cause for concern in the future.   

Anthropogenic disturbance: Although no known tourism targets this species in South Africa, tourism, boat traffic and ‘swim-with’ programmes are known to influence the natural movements (Constantine et al. 2004; Lusseau 2005), social behaviours (Nowacek et al. 2001; Bejder et al. 2006b; Rocha et al. 2023), energy budgets and geographic ranges (Bejder et al. 2006a) of bottlenose dolphin species. For example, a long-term study in New Zealand found an increase in dolphin avoidance of swimmers, and a decrease in dolphin interaction with humans over time. Additionally, cetaceans have shown additional avoidance behaviours in response to other forms of anthropogenic disturbance (Finley et al. 1990; Kruse 1991; Janik & Thompson 1996; Bejder et al. 1999), which may in turn affect natural foraging, resting and socialising behaviour (Constantine 2001; Constantine et al. 2004). Continued disruption of feeding, resting and social activities of Common Bottlenose Dolphins could have detrimental impacts on reproduction rates (Stensland & Berggren 2007; Dans et al. 2008) and calf survival (Bejder et al. 2006a; Stensland & Berggren 2007).

Collision with boats: Vessel-related physical injury of bottlenose dolphins has been documented across a number of regions (e.g. Nowacek et al. 2001; van Waerebeek et al. 2007; Bechdel et al. 2009; Dwyer et al. 2014), where collision with propellers and hulls may result in injuries ranging from minor lacerations and blunt force trauma to death. For example, photo-identification data captured off the coast of Florida showed that 6.0% of the distinctly marked population of bottlenose dolphins had injuries attributed to motorised vessels (Bechdel et al. 2009), and in the Gulf of Guayaquil, nearly 2% of bottlenose dolphins had propeller-related scars and injuries (van Waerebeek et al. 2007). Three fatally injured bottlenose dolphins off western Florida showed a range of injuries, including a completely severed tail and substantial bruising (Morgan & Patton 1990). In the Southern Hemisphere, van Waerebeek et al. (2007) found that habituation of dolphins to boats appears to be a contributing factor in dolphin-vessel collision events.

Fisheries bycatch: Accidental bycatch of Common Bottlenose Dolphins occurs throughout the species’ range in both commercial and recreational fisheries, as well as shark nets, but incidental reports are poorly documented (Wells & Scott 1999). As shark nets are deployed in shallow, coastal waters in South Africa, bycatch of offshore T. truncatus is not a problem within the assessment region. However, depredation (or the act of stealing or damaging prey captured in fishing gear) occurs in offshore commercial and local fishing areas and can lead to serious physical injury or death of cetaceans through entanglement or ingestion. Additionally, continued and learned behaviour associated with depredation impacts natural activity patterns (Cox et al. 2003; Lauriano et al. 2004; Brotons et al. 2008; Sigler et al. 2008; Powell & Wells 2011). Furthermore, dolphins often cause substantial economic impacts for fishermen, including net damage and a reduction in overall fish catch (Buscaino et al. 2009), leading to negative responses towards dolphins.

Competition: Depredation behaviour is likely a direct response to increased competition for forage resources between cetaceans and humans. Loss of prey availability and biomass as a result of overfishing and environmental degradation is an increasing threat to this species in large parts of its range.

Noise pollution: Cetaceans depend on auditory stimuli for navigation, communication and hunting, thus are commonly considered sensitive to anthropogenic noise pollution (Finneran et al. 2000). Noise associated with ships, seismic exploitation, marine construction, demolition and sonars affect the movements and diving patterns of cetaceans and disrupts their communicative pathways and behaviour (Buckstaff 2004; Branstetter et al. 2018; Kragh et al. 2019), and may result in negative physiological responses, such as increased stress (Nowacek et al. 2007; Koper & Plön 2012).

Environmental contaminants: Xenobiotic chemicals and their toxic effects threaten the reproductive potential and immune system of this species. Bioaccumulation of persistent organic pollutants (POPs) within the body tissues of top marine predators is common and is documented for this species (Yordy et al. 2010a, 2010b).

Climate change: Climate change has direct and indirect effects on marine species. Shifts in climatic conditions can alter the habitat range and distributions of dolphins, as well as prey species, and can exacerbate existing threats, such as habitat loss, bycatch, and pollutant concentrations. 

Current habitat trend: Declining in quality due to ongoing coastal development and poor agricultural practices upstream of watersheds. 

Conservation

The species is listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the Marine Living Resources Act (No. 18 of 1998). Mitigation measures designed to limit accidental cetacean bycatch in gillnet fisheries include spatiotemporal fishery closure regimes, marine protected areas, the use of acoustic alarms and other modifications of fishing equipment and techniques. Acoustic alarms often emit high frequency sounds, designed to deter cetaceans away from nets, or at least warn them of the barrier’s presence (Dawson et al. 1998). The use of high frequency alarms on gillnets along the US east coast were found to have only a subtle deterring effect on bottlenose dolphins and are unlikely to reduce dolphin bycatch to any significant degree (Cox et al. 2003). The use of pingers in artisanal fisheries around the Balearic Islands (western Mediterranean), reduced the level of interaction between bottlenose dolphins and bottom-set nets; however, the propensity for dolphin habituation calls for continued research into the long-term viability of acoustic deterrents, or the use of alternative mitigation efforts (Brotons et al. 2008). However, there is some evidence (Erbe et al. 2016) that pingers increase T. aduncus catch (no data for T. truncatus), and the potential for pingers to increase rather than decrease catch is a concern.

This species is likely to be impacted by offshore resource exploration (seismic surveys) and exploitation (for example, drilling and blasting), which has increased substantially in South African waters over the last decade. Working with environmental impact agencies to mitigate any impacts and applying pressure on governmental authorities to make accepted good practice mitigation measures obligatory during any exploration/exploitation, are important interventions.

Finally, in response to the increasing levels of negative impacts associated with the interaction between dolphins and the fishing industry, Buscaino et al. (2009) suggest a collaborative response towards sustainable exploitation of oceanic resources, a decrease in the intensity of marine extraction and the establishment of protected areas .

Recommendations for managers and practitioners: 

• Further field surveys to delimit geographical boundaries and identify threats. 

Research priorities: 

• Continued research into the taxonomic relationships and the genetic variation between these southern African populations is necessary. Genetic analyses to assess potential differences in population structure of bottlenose dolphins between South Africa’s west and east coasts, as well as those off Namibia. 
• Continued investigation into the response of bottlenose dolphins to anthropogenic sound. Including offshore petroleum exploration and exploitation. 
• Physiological and behavioural effects of anthropogenic pollution, including bioaccumulation of toxins, noise pollution and plastic debris to Common Bottlenose Dolphins within the assessment region. 
• Investigation into the direct and indirect impacts of climate change, particularly increasing sea temperatures, and how these can affect the population and distribution of Common Bottlenose Dolphins. 

Encouraged citizen actions: 

• Use information dispensed by the South African Sustainable Seafood Initiative to make good choices when buying fish in shops and restaurants, for example FishMS 0794998795. 
• Buy fresh produce that has been grown in pesticide-free environments. 
• Save electricity and fuel to mitigate CO₂ emissions and hence, the rate of climate change. 
• Buy local products that have not been shipped. 
• Report sightings on virtual museum platforms (for example, iNaturalist and MammalMAP) to help with mapping geographical distribution, and report any stranded dolphins to your nearest museum, the Centre for Dolphin Studies or to relevant local authorities. 

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